PROJECT SUMMARY Normal function of the lower urinary tract (LUT) requires coordination of neuronal activities to allow bladder filling for urine storage later followed by bladder contraction to accomplish emptying at an appropriate time and place. Despite the fact that much is known about the neuroanatomy and mature circuitry of the LUT, relatively little is known about the molecular composition, development and postnatal maturation of distinct neuron subtypes that regulate bladder contractility. At present we lack a catalog of receptors expressed by different types of pelvic ganglia neurons that could be used to investigate how these critical neurons reach their targets in different LUT organs or direct regenerative efforts in cases of surgical damage. Even less is known about the molecular makeup of chemosensory brush cells and paraneurons in the urethra that are positioned to modulate LUT contractility. These cells contain high levels of neurotransmitters and thus can act as neuromodulators that stimulate bladder contraction in response to infection or mechanical stretch. Knowledge of the connections between motor neurons in pelvic ganglia and these neuromodulatory cells would enable detailed mechanistic studies of bladder sensitization and contractility in response to infection, inflammation or urine composition. The overall goal of this GUDMAP Atlas project is to fill these gaps in knowledge so that future mechanistic studies can be pursued. Four Specific Aims are proposed: (1) compile an atlas of genes expressed by pelvic ganglia neurons at single cell resolution during development and postnatal maturation; (2) map the first appearance and distribution of urethral neuromodulatory cells during development in the mouse; (3) identify genetic markers for subsets of urethral neuromodulatory cells by RNA-seq ; (4) generate a detailed spatial and temporal map of nerve terminals between neuromodulatory cells and sensory or autonomic pelvic ganglia neurons. These studies will generate novel information that is current lacking from the GUDMAP database. Our results will be summarized in diagrams and tutorial maps on the GUDMAP site and the gene sets identified will expedite comparative studies in human tissues. As a result the research community will be able to investigate the functions of specific cell types and test hypotheses using cell type and gene specific approaches.